The present invention relates to a display device and a method of driving the display device, and, for example, to a liquid crystal display device of the so-called active matrix type and a method of driving the liquid crystal display device.
In an active matrix type liquid crystal display device, a liquid crystal layer is sandwiched between a pair of opposing substrates, formed on a liquid-crystal-layer-side surface of one of the pair of substrates are a plurality of gate signal lines extending in an x direction and arranged in a y direction, and a plurality of drain signal lines extending in the y direction and arranged in the x direction, and each of a plurality of pixel areas is defined by two adjacent ones of the gate signal lines and two adjacent ones of the drain signal lines.
Each pixel area is provided with a switching element driven by a scanning signal via a gate signal line, and is provided with a pixel electrode supplied with a video signal via the switching element from a drain signal line. The respective gate signal lines are successively selected by the scanning signals, and the respective signal lines are supplied with video signals in synchronism with the selection of the gate signal lines such that images are produced in a liquid crystal display section formed by a plurality of pixel areas.
There are various techniques for displaying gray scales at each of the pixels of such liquid crystal display devices. One is to vary the amplitude of a voltage applied to a pixel in accordance with a desired gray scale level, and this technique is widely used in present liquid crystal display devices employing TFTs (Thin Film Transistors). Another technique is PWM (Pulse Width Modulation) which reproduces a gray scale representation by varying the duration of a pulse applied to a pixel while the amplitude of the pulse is kept constant.